This invention relates to an apparatus for controlling an elevator and, more particularly, to an elevator controller employing a microcomputer for executing several kinds of controls.
In recent years, several kinds of microcomputers or microprocessor units (hereinafter, MPUs) have been developed as the technology of semiconductors has rapidly advanced. In many industrial machines and devices, sophisticated controls are implemented by using MPUs in their control units. Since many complicated controls are required in elevator systems, elevator controls also are shifting to a control with an MPU, as shown in FIG. 7 which is similar to Japanese Application Publication 59(1984)-22869 published on Feb. 6, 1984. U.S. Pat. No. 4,456,096 also shows an elevator control system using an MPU.
In FIG. 7, input and output terminals of an MPU 1 are connected to an input-output circuit 2. Amplifier 3 amplifies output signals from an output port PO1 of the input-output circuit 2. A three-phase AC power source 4 is connected to a control circuit 6 for controlling a traction motor 8 through a contact 5a of a starting contactor or relay 5. The motor control circuit 6 controls the power supplied to the motor 8 in accordance with the output signal from the amplifier 3. Current detector 7 detects the current supplied to the motor 8 through the motor control circuit 6, and a corresponding output signal from the detector 7 is supplied to an input port PI1 of the input-output circuit 2. A speed detector 9, such as a tachometer, connected to the rotary shaft of the traction motor 8, detects the speed of the motor 8 and supplies a corresponding output signal to an input port PI2 of the circuit 2. An MPU checking circuit 10 is connected to an input port PO2 of the circuit 2 and has an output terminal connected to a relay 11. A switch 12, for commanding the travel of the elevator, is connected to an input port PI3. A check switch 13 is connected to an input port PI4 of the circuit 2 and is provided for checking the operation of the MPU checking circuit 10. A relay 14, for commanding an emergency stop of the elevator, is connected to an output port PO3 of the circuit 2.
In the operation of the above apparatus, when the starting contactor 5 for activating the apparatus is energized, the contact 5a of the contactor is closed, and the motor control circuit 6 is enabled for operation. When the command switch 12 is closed in order to start the travel of an elevator, the output signal of the switch 12 is inputted to the MPU 1 through the input-output circuit 2, and then the MPU 1 executes a calculation to calculate the difference between the output signal from the speed detector 9 and a speed reference value. The difference signal of the calculation is fed to the amplifier 3 through the input-output circuit 2 to be amplified and supplied to the motor control circuit 6 as a control signal. The motor control circuit 6 controls the power to be supplied to the motor 8 in accordance with the control signal from the amplifier 3, which signal is indicative of the difference between the rotating speed of the motor 8 and the present reference value, so that the traction motor 8 varies its speed in accordance with a predetermined speed reference pattern. When the MPU 1 detects an abnormal speed or an abnormal current, the MPU 1 operates the relay 14 by way of the input-output circuit 2 to cause an emergency stop of the elevator.
In case the MPU 1, itself, malfunctions, a very dangerous situation arises because the MPU 1 checks all controls and abnormal operations. Therefore, in an elevator control with an MPU, it is necessry also to check the operation of the MPU itself. The checking circuit 10 is provided for checking the operation of the MPU 1. When the MPU is operating normally, the checking circuit 10 continually supplies a signal to maintain relay 11 picked-up or energized. However, the checking circuit 10 stops outputting the signal when the MPU operates abnormally, so that the relay 11 drops out (is de-energized) to make the emergency stop.
Since an elevator carries human beings, it must operate absolutely safely and correctly. Accordingly, an authorized person must periodically check the operation of the MPU 1 at predetermined times. The check switch 13 is provided for checking the operation of the MPU itself.
When the check switch 13 is closed by an authorized person, an artificial signal, representing abnormal operation of the MPU 1, is fed to the MPU checking circuit 10. If the MPU checking circuit 10 is in a normal condition, the MPU checking circuit 10 operates almost simultaneously with the operation of the switch 13 to cause the relay 11 to drop out, thereby confirming the normal operation of the MPU checking circuit 10. Then, switch 13 may be re-opened to permit operation of the elevator system. If the relay 11 does not simultaneously drop out, then a fault in the MPU is indicated.
However, in the above conventional apparatus with an MPU, this manual operation check must be periodically executed at predetermined times which may be as long as a half month or a month apart, thereby requiring expensive manpower. Furthermore, there is the problem that malfunctions arising between the operation checks will not be detected.